There are three basic driver air bag cover shapes that are used in vehicles: a round shape, a rectangular shape, and a triangular shape. The shape, in large measure, is influenced by the spoke location on the steering wheel.
Currently driver air bag internals are designed for each cover shape in which they are placed. For instance, the cushion pack and the module base plate are the shape of the outer cover. This makes it impossible to use radically different cover shapes with common air bag internals.
There have been attempts to provide one or more secondary escape paths in the cover to allow the cushion to deploy laterally. This approach complicates using different cover shapes with common module internals because the secondary cover tear seams and compatible cushion pack folds place additional constraints on the design. As vehicle development times are shortened, more styling freedom is needed.